Non parametric zero replacement strategies
Non parametric zero replacement strategies.
zeroreplace(x, a = 0.65, delta = NULL, type = "multiplicative")
x |
A matrix with the compositional data. |
a |
The replacement value (δ) will be "a" times the minimum value observed in the compositional data. |
delta |
Unless you specify the replacement value δ here. |
type |
This can be any of "multiplicative", "additive" or "simple". See the references for more details. |
The "additive" is the zero replacement strategy suggested in Aitchison (1986, pg. 269). All of the three strategies can be found in Martin-Fernandez et al. (2003).
A matrix with the zero replaced compositional data.
Michail Tsagris
R implementation and documentation: Michail Tsagris mtsagris@uoc.gr
Martin-Fernandez J. A., Barcelo-Vidal C. & Pawlowsky-Glahn, V. (2003). Dealing with zeros and missing values in compositional data sets using nonparametric imputation. Mathematical Geology, 35(3): 253-278.
Aitchison J. (1986). The statistical analysis of compositional data. Chapman & Hall.
x <- as.matrix(iris[1:20, 1:4]) x <- x/ rowSums(x) x[ sample(1:20, 4), sample(1:4, 1) ] <- 0 x <- x / rowSums(x) zeroreplace(x)
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